• Communications for Statistical Applications and Methods
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• 제5권2호
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• pp.373-381
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• 1998

In this paper a new control chart which accounts for correlation between process subgroups will be proposed. We consider the case where the process fluctuations are autocorrelated by a stationary AR(1) time series and where n($\geq1$) items are sampled from the process at each sampling time. A simulation study is presented and shows that for correlated subgroups, the proposed control chart makes a significant improvement over the traditionally employed X-bar chart which ignores subgroup correlations. Finally, we illustrate the proposed chart by comparing the standardized residuals and X-bar chart on a data set of motor shaft diameters.

• 공학교육연구
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• 제15권1호
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• pp.3-8
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• 2012

This study present the standard flow chart for civil engineering considering Korean education environment. The flow charts of USA's 20 universities and Korea's 6 universities are investigated. The standard flow chart are proposed based on the standard curriculum of civil engineering and flow charts of USA and Korea though analyzing of prerequisite of each subject. The proposed standard flow chart is expected when used to improve korean universities curriculum.

• 대한산업공학회지
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• 제38권4호
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• pp.237-243
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• 2012

This paper proposes quantitative investment strategies for KOSPI200 index futures using VKOSPI and control chart. Stochastic control chart is employed to decide when to take a position as well as what position out of long and short should be taken by monitoring whether VKOSPI or difference of VKOSPI touches the control limit lines. The strategies include 4 approaches, which are traditional control chart and 2-Area control chart coupled with VKOSPI and its difference, respectively. Computational experiments using real KOSPI200 futures index for recent 3 years are conducted to show the excellence of the proposed investment strategies under control chart framework.

• 대한안전경영과학회지
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• 제14권3호
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• pp.167-174
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• 2012

In the manufacturing process the most widely used $\bar{X}$ chart has been applied to control the process mean. Also, Accelerated Life Test(ALT) is commonly used for efficient assurance of product life in development phases, which can be applied in production reliability acceptance test. When life data has lognormal distribution, through censored ALT design so that censored ALT data has asymptotic normal distribution, $ALT\bar{X}$ control chart integrating $\bar{X}$ chart and ALT procedure could be applied to control the mean of process in the manufacturing process. In the situation that process variation is controlled, $Z_p$ control chart is an effective method for the very small fraction nonconforming of quality characteristic. A simultaneous control scheme with $ALT\bar{X}$ control chart and $Z_p$ control chart is designed for the very small fraction nonconforming of product lifetime.

• Communications for Statistical Applications and Methods
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• 제21권1호
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• pp.69-80
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• 2014

This paper considers the problem of monitoring the mean of a normally distributed process variable when the objective is to effectively detect both a sustained shift and a linear drift. The design and application of a generalized likelihood ratio (GLR) chart for simultaneously monitoring a sustained shift and a linear drift are evaluated. The GLR chart has the advantage that when we design this chart, we do not need to specify the size of the parameter change. The performance of the GLR chart is compared with that of other control charts, such as the standard cumulative sum (CUSUM) charts and the cumulative score (CUSCORE) charts. And we compare the proposed GLR chart with the GLR charts designed for monitoring only a sustained shift and for monitoring only a linear drift. Finally, we also compare the proposed GLR chart with the chart combinations. We show that the proposed GLR chart has better overall performance for a wide range of shift sizes and drift rates relative to other control charts, when a special cause produces a sustained shift and/or a linear drift in the process mean.

• 한국안광학회지
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• 제13권4호
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• pp.115-119
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• 2008

목적: 노안에서 십자와 적록을 조합한 시표를 사용하여 얻어진 잠정가입도와 최종가입도를 비교하기 위해 실시하였다. 방법: 대상자는 41~60세(평균연령 51.7세) 사이의 노안이 있는 60명으로 하였다. 잠정가입도는 십자시표(CG), 적록시표(RG) 및 두 가지 시표를 조합하여 만든 적록십자시표(RGCG)를 사용하여 결정하였으며, 최종가입도는 검사거리 40 cm에서 각 대상자에 맞게 잠정가입도를 조정하여 결정하였다. 결과: 측정 방법별 잠정가입도와 최종가입도 사이의 유의한 차이가 있었으며, 적록십자시표에 의한 방법이 높은 신뢰도(repeatability)를 나타냈다. 결론: 적록 십자시표(RGCG)는 노안 가입도 결정에 필요한 적절한 데이터를 얻을 수 있으며, 양안시 임상에서 가입도 처방의 진단 평가에 유용할 것이다.

• 한국환경복원기술학회지
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• 제7권5호
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• pp.1-11
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• 2004

The purposes of this study are to revise an site-based environmental education(EE) Program evaluation chart and to evaluate site-based EE programs using the chart. For revising the evaluation chart, several elements in the former chart were changed, infused, deleted, integrated, or split. The points of some elements in the former chart were also changed. The revised chart consist of 38 elements in 6 areas: purpose and goal, teaching and learning plan, teaching and learning process, educational effect and programs evaluation, Program characteristic, and program operation. Using the revised chart, the researchers evaluated 159 site-based EE programs, funded by the Korean Ministry of Environment in 2002. The result indicated that the mark of 'teaching and learning plan' area is higher than other areas, while the mark of 'educational effect and programs evaluation' is the lowest. On the basis of evaluation, the researchers offered some recommendations for the Korean site-based EE programs.

• International Journal of Quality Innovation
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• 제7권3호
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• pp.107-115
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• 2006

Control charts are important tools of statistical quality control. In 1956, Duncan first proposed the economic design of $\bar{x}-control$ charts to control normal process means and insure that the economic design control chart actually has a lower cost, compared with a Shewhart control chart. An moving average (MA) control chart is more effective than a Shewhart control chart in detecting small process shifts and is considered by some to be simpler to implement than the CUSUM. An economic design of MA control chart has also been proposed in 2005. The weaknesses to only the economic design are poor statistics because it dose not consider type I or type II errors and average time to signal when selecting design parameters for control chart. This paper provides a construction of an economic-statistical model to determine the optimal parameters of an MA control chart to improve economic design. A numerical example is employed to demonstrate the model's working and its sensitivity analysis is also provided.

• Journal of the Korean Data and Information Science Society
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• 제10권1호
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• pp.233-241
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• 1999

본 논문에서는 공정평균을 관리하기 위한 관리도로서 지수가중 이동평균(EWMA)관리도를 고려하였다. 기존의 표본평균에 기초한 관리도의 비로버스트성 (non-robustness)에 근거하여 공정평균의 로버스트 추정량인 M-추정량에 기초한 지수가중 이동평균 관리도를 제안하였다. 제안된 관리도의 성능을 기존의 관리도와 비교해 보기 위하여 다양한 상황에서 모의실험을 행하였으며, 실험결과 제안된 관리도의 우수성이 입증되었다.

• Journal of the Korean Data and Information Science Society
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• 제26권4호
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• pp.997-1006
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• 2015

In industrial quality control, when engineers use VSI control procedure they should consider both required time to signal and switching behaviors together in the case of production process changed. Up to the present, many researchers have studied fixed sampling interval (FSI) chart and variable sampling interval (VSI) chart in the points of average number of samples to signal (ANSS) and average time to signal (ATS). However, ANSS and ATS do not provide any switching information between different sampling intervals of VSI schemes. In this study, performances of two sampling intervals VSI chart and three sampling intervals VSI chart are evaluated and compared. The numerical results show that ANSS and ATS values of two sampling intervals VSI chart and three sampling interval VSI chart are similar regardless the amount of shifts. However, the values of switching behaviors including ANSW are less efficient in three sampling intervals VSI charts than in two sampling intervals VSI chart.